By Keith Gauldin, Wildlife Biologist, Alabama Division of Wildlife and Freshwater Fisheries
The coastal marshes in southwest Alabama provide valuable habitat to a wide array of wildlife. One of the more unique species found in this area is the Mississippi diamondback terrapin (Malaclemys terrapin pileata).
While there are seven different subspecies of diamondback terrapins, the Mississippi diamondback terrapin is the one that calls Alabama home. Their distribution is restricted to coastal marshes extending from the Florida Panhandle to eastern Louisiana. In Alabama, they primarily occupy the salt marshes and estuaries of Mississippi Sound. Much of this habitat can be viewed to the west of Dauphin Island Parkway prior to crossing the bridge over Mississippi Sound to Dauphin Island at Cedar Point, on the isolated islands in Mississippi Sound and along the coastline of the Grand Bay Savannah Forever Wild Tract.
This medium-sized turtle ranges in length from 5 to 9 inches, with the females being the larger of the sexes. The carapace (shell) is gray to black and marked with concentric growth rings on the scutes (scales) with a yellow to creamy colored ring around the perimeter of the carapace.
The head and neck of the terrapin are much more robust and thicker than other turtles. This anatomical feature enables it to utilize well-developed jaws and muscles to crush the hard shells of snails, clams and mussels, which are primary food items for the turtle.
Diamondback terrapins have some interesting characteristics that make them well-suited to reside in their brackish environment. The most unique is the physiological adaptation of the lachrymal gland--the gland that produces tears. The gland is utilized by the terrapin to secrete salts so it can regulate its salt levels. It also has the ability to determine salinity concentrations in the water to efficiently hydrate itself with fresh water. As rain falls on brackish water during a storm, there is a brief period in which this turtle will swim high in the water column to drink from the freshwater level prior to it diffusing into the saline water below.
The female terrapins begin to seek suitable nesting sites in early spring. In early April through May, females begin excavating nests on isolated shell hash beaches above the high tide mark. They typically lay five to 12 eggs per nest and continue doing so throughout the season, producing two to five clutches.
Unfortunately, they succumb to high rates of predation by raccoons excavating the nests. Once hatched, they become targets for a myriad of predators including wading birds, raccoons, feral cats, gulls and crows.
While not allowed today, terrapins were nearly driven to extinction due to commercial harvests. Their meat was used as the primary ingredient in turtle soup and was in great demand during the late 1800s and early 1900s. Many local populations were decimated from the over-harvest of this fashionable delicacy. Even early locals on Dauphin Island were in on the trade, developing a substantial terrapin farm facility that housed locally-caught terrapins for the commercial trade.
Although the commercial harvest is long gone, terrapins continue to endure many hardships. Lack of suitable nest sites, nest predation, and the inadvertent drowning in crab traps are the most apparent hurdles that are limiting populations in Alabama. Localized surveys have revealed that the terrapin numbers in coastal Alabama have apparently declined in recent years. However, contemporary research is revealing more crucial information that will increase our understanding of this unique creature and allow for better management decisions concerning the future and fate of this turtle of the salt marsh.